Advances in the development and improvements of the luminous flux of light-emitting devices such as solid-state semiconductor and organic light-emitting diodes (LEDs) have made these devices suitable for use in general illumination applications, including architectural, entertainment, and roadway lighting. Light-emitting diodes are becoming increasingly competitive with light sources such as incandescent, fluorescent, and high-intensity discharge lamps. Also, with the increasing selection of LED wavelengths to choose from, white light and colour changing LED light sources are becoming more popular.
The following provide examples of such light sources. In U.S. Pat. Nos. 5,803,579 and 6,523,976, an illuminator assembly incorporating light emitting diodes is described as having a plurality of LEDs on a vehicular support member in a manner such that, when all of the LEDs are energised, illumination exhibiting a first perceived hue (e.g., blue-green) and projected from at least one of the LEDs, overlaps and mixes with illumination exhibiting a second perceived hue (e.g., amber), which is distinct from said first perceived hue and which is projected from at least one of the remaining LEDs in such a manner that this overlapped and mixed illumination forms a metameric white colour and has sufficient intensity and colour rendering qualities to be an effective illuminator.
In U.S. Pat. No. 6,513,949, LED/Phosphor-LED hybrid lighting systems for producing white light are described as including at least one light emitting diode and phosphor-light emitting diode. The hybrid lighting system exhibits improved performance over conventional LED lighting systems that use LEDs or phosphor-LEDs to produce white light. In particular, the hybrid system permits different lighting system performance parameters to be addressed and optimised as deemed important, by varying the colour and number of the LEDs and/or the phosphor of the phosphor LED.
In U.S. Pat. No. 7,014,336, systems and methods for generating and modulating illumination conditions are disclosed to generate high-quality light of a desired and controllable colour, for creating lighting fixtures for producing light in desirable and reproducible colours, and for modifying the colour temperature or colour shade of light within a pre-specified range after a lighting fixture is constructed. In one embodiment, LED lighting units capable of generating light of a range of colours are used to provide light or supplement ambient light to afford lighting conditions suitable for a wide range of applications.
In the above and other such light sources, by varying the relative power with which the individual LEDs of the light source are driven, it may become possible to vary the colour output of the light source. Likewise, by varying the overall power supplied to each LED, it becomes possible to vary the combined output intensity of the light source. When all the LEDs within the light source are driven to their respective maximum intensity, however, the combined spectral output does not generally correspond to a desired output, such as for example the white point at the centre of the CIE 1931 colour space chromaticity diagram. This often results from the fact that differently coloured LEDs generally have different output intensities and efficiencies. As such, the range of colours in these light sources for which maximum light output is achievable is biased to one or more of the constituent LED colours in the package(s) or cluster(s), generally the LED colour(s) having a higher output efficiency and/or capacity.
Consequently, it is generally not possible with currently available light sources to select a minimal number of LEDs (e.g. three LEDs in an RGB light source or package, or four LEDs in an RAGB light source or package) to minimise manufacturing costs while having each LED operate at an optimal output intensity such that a combined maximum output thereof is substantially centred at the white point of the CIE 1931 colour space chromaticity diagram, or around other such desirable combined outputs. For instance, this situation may also apply when designing light sources for which an optimal output intensity at a given colour, or within a given colour range, is desired.
Therefore, there is a need for an improved light source and lighting system that overcomes some of the drawbacks of the above and other known light sources.
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.